This invention relates to a variable capacity flywheel to be mounted to the rotary system of an internal combustion engine used, for example, in motorcycles, automobiles, etc. In internal combustion engines, flywheels have been used to restrict within a predetermined value the variations of angular velocity which occur during operation due to changes in torque. The momentum of a body of revolution may be expressed as E=I.omega..sub.m, that is, as the product of the moment of inertia I of the body of revolution and an average angular velocity .omega..sub.m. Since the momentum of a body of revolution increases with increasing rotational speed, an internal combustion engine needs a flywheel having a large moment of inertia I in the range of low engine speed, but it needs a flywheel having a comparatively small inertia of moment in the range of high engine speed. Additionally, from the standpoint of accelerating and decelerating ability at high engine speeds, it is preferable for the moment of inertia I to be small. To meet these diverse requirements, variable capacity flywheels have been developed.
A variable capacity flywheel in a conventional system uses an auxiliary flywheel connected to a flywheel directly coupled with a crank shaft through a centrifugal clutch. In these systems, a significant amount of slippage exists between both flywheels in engaging or disengaging the clutch at the boundaries of specified engine speeds. This results in a great loss of power in the system.
Furthermore, a variable capacity flywheel in a conventional system uses a main flywheel engaged with an auxiliary flywheel by energizing an electromagnetic clutch. This requires a large capacity battery or generator to actuate the electromagnetic clutch in the range of low engine speed. Such devices are therefore unsuitable for vehicles of a small total stroke volume or for those which require quick acceleration and responsive handling.